I have had luck using "Bar Keepers Friend" or "Bon Ami". You can find them at Wal-Mart or your local grocery store where the sell kitchen cleaning supplies. These are non abrasive cleaner, kind of like Ajax but without the abrasiveness. Wet the glass and sprinkle a small amount of cleaner on it and use some 00 steel wool. Apply a little pressure and rub in a circular motion. Rinse with clean water, and it should look like new.